Patients with inborn metabolic diseases are normally treated with a protein restricted diet. Such diet eliminates all foods originating from animal origin (milk, meet, fish, eggs, etc.). From birth on, these patients are therefore dependent of specifically designed medical foods.
The dietary management of many inborn metabolic diseases requires the absence of specific amino acids. For instance, phenylketonuria (PKU) patients require protein sources with as low as possible concentrations of phenylalanine. For many years enteral formulas have been developed that are based on free amino acids blended into a nutritional complete amino acid composition, but without the specific amino acid that the patient is unable to metabolize, e.g. phenylalanine in PKU patients. Other inborn metabolic diseases may require a different amino acid profile.
The free amino acid based formulas generally suffer from the problem that the taste is perceived as bad. Particularly when patients become older, palatability issues become more of a problem, which significantly impairs compliance with the product, which may lead to poor nutritional intakes or too high intakes of the amino acid that cannot be metabolized. Ultimately, this may affect neurological development of the patients.
U.S. Pat. No. 5,411,757 discloses food supplements to be added to low protein natural foods with up to 100% of certain unpalatable acidic L-amino acids: L-glutamic acid, L-aspartic acid, L-arginine, and L-methionine, replaced by their more palatable counterparts: L-glutamine, L-asparagine, L-citrulline, and L-cystine, respectively. In addition the supplement contains the mentioned amino acids in as low concentration as nutritionally possible in order not to affect the taste of the food to which the amino acids are added.
EP 2205100 relates to the same problem of bad taste in hydrolysed and amino acid based infant formulas and it describes a method for decreasing the bitterness of a protein-free infant formula. The method may comprise intermixing a protein equivalent source, a carbohydrate source, a fat source, vitamins, and minerals in a solution and adding sodium hydroxide or potassium hydroxide to adjust the pH of the formula to between 6.5 and 7.2. It is asserted that the addition has a positive effect on taste.
Taking taste concerns into account, many products are available on the market, such as Anamix (PKU), ANC Phenylade, PKU gel (Vitaflo/Nestle), XpheKid (MetaX), Phenex2 (Abbott) and Phenylfree 2 (Mead Johnson). All of these products are nevertheless troubled by a bitter or bad taste, at least to some extent, as shown in Table 1. In the art there is thus a need for improving the taste of these lines of nutritional products.